1. Technical Field
The present invention relates generally to a diving information processing device and to a control method and a control program for a diving information processing device, and relates more particularly to technology for preventing a drop in the reliability of diving information resulting from erroneously entering the diving mode.
2. Related Art
Information devices having functions for measuring water depth and keeping time are commonly used when diving. Diving information processing devices, also referred to as dive computers, have functions for measuring change in water pressure while diving and change in air pressure when flying based on these measurements and simulating tissue absorption and elimination of inert gases (particularly nitrogen), also called in-gassing and out-gassing, so that the diver can dive safely and avoid decompression sickness.
As taught in Japanese Unexamined Patent Appl. Pub. H8-327355A, a dive computer with a depth gauge measures the air pressure at a predetermined time interval, automatically enters the diving mode from any display mode when conductivity is detected as a result of a water detection switch composed of two electrodes entering water, and starts measuring water depth at a predetermined time interval based on the air pressure when the diving mode was entered to denote 0 meters. If water entry is detected, a water depth exceeding a predetermined threshold is then detected, and the water detection switch then remains continuously off, the diving mode is cancelled and the time is displayed. After water entry is detected and the predetermined depth is detected, an on-switch counting circuit also checks the on/off status of the water detection switch, blocks entering the diving mode if the water detection switch is off, and continues displaying the time.
However, temporary opening of the water detection switch may be detected as a result of bubbles in the air exhaled by the diver or the formation of an insulation layer on the surface of the conductivity switch contacts that detect water entry even after the predetermined diving depth is detected after diving starts, and this can prevent displaying the diving information even though the diver is still in the water. This is a fatal problem for an information device that is relied upon by the diver for safe diving management.
The water detection switch may also detect conductivity when not diving as a result of the dive computer being placed with other wet items or even simply being worn in contact with the body. If the diving mode is wrongly entered due to such detection of conductivity while the user is at a high altitude, such as when flying, and the air pressure then changes due to a drop in altitude, the pressure difference may be erroneously measured and displayed as an increase in water depth.
If the diving mode is simply cleared and the display is restored to the state before high altitude movement, all tissue in/out-gassing calculations will be cleared, the effect of the change in air pressure due to travel at high altitude on the body will not be considered by the diving mode, and the advantage of using a portable device, specifically the ability to continuously measure and calculate tissue in/out-gassing based on the measurements, is lost.
The diving information processing device and the control method and control program for a diving information processing device according to the present invention enable recognizing if the diving mode is erroneously entered while travelling at high altitude so that calculating tissue in/out-gassing of inert gases can continue.